Flexible endoscopy is a ubiquitous means of diagnosis and therapy in nearly all aspects of medicine, including ureteroscopy, colonoscopy, gastroscopy, duodenoscopy, bronchoscopy, ventriculoscopy, and sinus endoscopy. Endoscopic systems from the major manufacturers are very similar with controls based on simple flexion of the tip of the endoscope, rotational control, and in and out translational movement. These three movements are controlled by the operator at the head of the instrument and are all distinct in their character, making intuitive control difficult to learn and perform. Efficient and safe control could be enhanced by a control interface that permits intuitive movements with faithful visual feedback (e.g. when a target is identified, it can be reached smoothly). Because of the complexity of movements needed for many applications, an integrated movement/control system would have the potential to greatly enhance the safety, efficacy, and efficiency of these instruments. While physicians who do endoscopy every day become quite skilled at the contortions that can be needed for effective placement of the instrument tip, the shortcomings of the current approach extend the time required for procedures [Harewood 2008], increase user fatigue [Berguer 2007], and have the potential to increase the frequency of errors. For those physicians who perform endoscopy on an occasional basis, the need for a more user-friendly, intuitive means of control becomes even more pronounced.
The basic design and functionality of all flexible endoscopes is similar, with differences dependent upon size. Smaller instruments have simpler but more limited control mechanisms with fewer degrees of freedom. Uretero-renoscopy is often performed with flexible ureteroscopes for access and manipulation in the ureter and kidney. Uses include stone removal, diagnosis for bleeding or malignancy, as well as direct biopsy and destruction of malignant lesions. In stone disease, ureteroscopy is becoming more widely used than the other minimally invasive means to remove stones in both adults and children [Kerbl 2002]. Ureteroscopes have improved in visual acuity and have become small enough to minimize trauma and permit use in small children. They have greater flexion capacity but remain controlled by the basic three-function mechanisms. Control is performed with two hands, one to move the ureteroscope in and out, and the other to rotate and flex the ureteroscope. This leaves no hand free to perform manipulations through the working port, which can include stone basketing, laser lithotripsy, tumor fulguration, or biopsy. In many clinical situations, the entire interior of the kidney must be carefully inspected to avoid leaving stone fragments or residual tumor. This requires moving the ureteroscope into each of the 10 to 12 calyces in the human kidney. Such delicate control requires significant skill and is often challenging and slow, even for the experienced endoscopist, particularly in the lower pole of the kidney where the instrument must be tightly flexed and then rotated and pulled back to move into the lower calyces.
Manipulation of the endoscope can be challenging, even for experienced physicians. The physician is typically watching the video image from the endoscope, while trying to navigate the anatomy. The physician must make the mental map from the anatomy to control the endoscope, which is often complex. Development of an effective and intuitive control system based on the visual image and directionality of the endoscope would be of great value in enhancing safety, efficiency, and efficacy of these procedures. It is well documented that more complex procedures require more time endoscopically and may have to be staged due to time constraints [Schuster 2001]. Particularly with regard to ureteroscopy, minimizing the time of the procedure is important since injury to the interior of the kidney may occur with ongoing ureteroscope manipulation and infusion of irrigating fluid to provide a clear view. With the complex movements needed to direct the ureteroscope tip to a particular location, the orientation of the visual field changes, which disorients the operator and renders the combination of movements needed to achieve the required direction not intuitively apparent. The complex choreography of movements needed to direct the ureteroscope into the various parts of the kidney is neither ergonomic nor efficient.
The importance of positional information through navigation has been recognized for many years, but there remains no clinically effective system for instrument navigation in the abdomen or urinary tract. This importance has been described with reference to the needs of natural orifice transluminal endoscopic surgery (NOTES) [Rasswiler et al. 2009]. Endoscopic procedures necessarily imply limitations in perception and spatial orientation of tools. Left unresolved, these limitations give rise to surgical complications. Fernández-Esparrach et al. conducted animal studies to assess the role of CT-based navigation for NOTES. This study resulted in minor complications in 40% of standard approach procedures, compared with 13% in procedures employing navigation through preoperative CT-based image registration [Fernández-Esparrach et al. 2010].
Several groups have investigated navigation in flexible endoscopy, but there is currently no commercially available system that integrates a robotic-like control system with flexible endoscopy. The Hansen Medical robotic catheter system (Sensei, Hansen Medical, Mountainview, Calif.) is most similar in concept, but drives a passive catheter element and relies solely on visual feedback. Initially developed for intracardiac electrophysiologic applications, a modified system was used to perform flexible uretero-renoscopy in swine [Desai et al. 2008]. This modified system was recently extended to humans in an 18 patient study of laser lithotripsy for renal calculi [Desai et al. 2011]. This system, while similar in principle, uses a steerable guide catheter and sheath assembly to control catheter placement. Limitations with such an approach include lack of intuitive control and positional information. In summary, we are not aware of any system that provides the capabilities of precision device manipulation proposed here by providing a “snap-in capability” for existing endoscopes as described below.